fix(zitadel): LDAP binding error with non-ASCII characters in DN (#10578)

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# Which Problems Are Solved

LDAP binding with non-ASCII characters in DN

# How the Problems Are Solved

The root of the problem is that ParseDN() function messes DN with
non-ASCII character. Instead of using DN object, returned from ParseDN
we use user.DN in binding request. ParseDN stays only for verifying
correctness of DN.

# Additional Context
- Closes #9970

---------

Co-authored-by: Stefan Benz <46600784+stebenz@users.noreply.github.com>
(cherry picked from commit 3a91b409c4)

internal/idp/providers/ldap/session.go

@@ -216,12 +216,12 @@ func trySearchAndUserBind(
 
 	user := sr.Entries[0]
 	// Bind as the user to verify their password
-	userDN, err := ldap.ParseDN(user.DN)
+	_, err = ldap.ParseDN(user.DN)
 	if err != nil {
 		logging.WithFields("userDN", user.DN).WithError(err).Info("ldap user parse DN failed")
 		return nil, err
 	}
-	if err = conn.Bind(userDN.String(), password); err != nil {
+	if err = conn.Bind(user.DN, password); err != nil {
 		logging.WithFields("userDN", user.DN).WithError(err).Info("ldap user bind failed")
 		return nil, ErrFailedLogin
 	}